Dometic Hot Water Heater Not Working

[jyh818]

On my recent trip, my hot water heater would not come on either electric or propane. Going through the internet I found ways to diagnose. Here is what I found thus far:

DC power coming from the switch inside the rig only shows 4.5V for either electric or propane. I read it should be 12V. I wonder why?

Thermostat and ECO and thermo resister all show connectivity.

My issue most likely is the control panel inside is only sending 4.5V. Both toggle switches light up when turning it on, but only sending 4.5V and not 12V.

Is there something in the control panel I can check? Could I quickly use a 12V battery and send 12V to the circuit to see if the propane lights? Will I fry anything doing this? Thanks in advance for any help.

Edit: Coach batteries are 12.5V. When on shore power, I get 5.5V.

My rig is 2021 Redhawk 31F

 

[SmokeyBear-JAY]

I know we may be comparing apples to oranges. You don't say what your rig is, years, etc. Mine is a 1998 so it may be a lot "simpler" than yours. On a trip in October, my refrigerator and water heater quit I did the same as you and found I had no DCV coming to fridge. Couldn't find the problem. When I got home, I took it to an RV repair place. Within the hour they had it diagnosed and fixed. It was a blown fuse hidden behind a screwed-on panel, somewhere I would have never thought to look. I saved myself hours of frustration by taking it in; well worth the one-hour labor. Sounds like you may have a similar problem.

 

[jyh818]

I do have DC voltage going into the water heater. It's only 4.5V and not 12V. If there's a faulty switch, why both the electric and propane switches go bad? I am thinking there's something from the control panel switch to the water heater that is restricting voltage.

 

[Grumpy]

I do have DC voltage going into the water heater. It's only 4.5V and not 12V. If there's a faulty switch, why both the electric and propane switches go bad? I am thinking there's something from the control panel switch to the water heater that is restricting voltage.

Have you checked the ground at the water heater? Where are you connecting the ground for your meter?

 

[JimD]

I have attached some info that may help. Good luck!

 

[jyh818]

Have you checked the ground at the water heater? Where are you connecting the ground for your meter?

Big shout out to Grumpy. He gave me a suggestion to check the ground. I used the frame of the heater when I initially checked the voltage, not realizing that the ground from the heater to the coach came loose or undone.

I ran a wire from the negative terminal of the coach battery to the frame of the heater to test and it fired right up. For the fix, I ran a wire from the refrigerator frame to the ground wire of the heater.

The ground for the heater was originally Wago nutted to a white wire that lead to a spaghetti mess of wiring where it was nearly impossible to find where it came loose. There were at least a half dozen other white wires. Quickest way was to just use a known ground nearby.

 

[norty1]

Yes, Grumpy seems to be well grounded!

 

[Ozzie D Odyssey]

If you haven’t figured it out already, the thermal fuse can/will act up too. See my write up here: https://www.jaycoowners.com/forums/f34/the-dreaded-death-of-the-dometic-water-heater-108140.html